package com.atguigu.distributed.lock.leecode;

import java.util.HashMap;
import java.util.Map;

public class LRUCacheDemo {
    //map负责查找，构建一个虚拟的双向链表，它里面安装的就是一个个Node节点，作为数据载体
    class Node<K, V> {
        K key;
        V value;
        Node<K, V> prev;
        Node<K, V> next;

        public Node() {
            this.prev = this.next = null;
        }

        public Node(K key, V value) {
            this.key = key;
            this.value = value;
            this.prev = this.next = null;
        }
    }

    //2 构建一个虚拟的双向链表，里面安放的就是我们的Node
    class DoubleLinkedList<K, V> {
        Node<K, V> head;
        Node<K, V> tail;

        //2.1构造方法
        public DoubleLinkedList() {
            head = new Node<>();
            tail = new Node<>();
            head.next = tail;
            tail.prev = null;
        }

        //2.2添加到头
        public void addHead(Node<K, V> node) {
            node.next = head.next;
            node.prev = head;
            head.next.prev = node;
            head.next = node;
        }

        //2.3删除节点
        public void removeNode(Node<K, V> node) {
            node.next.prev = node.prev;
            node.prev.next = node.next;
            node.next = null;
            node.prev = null;
        }

        //2.4 获得最后一个节点
        public Node getLast() {
            return tail.prev;
        }
    }

    private int cacheSize;
    Map<Integer, Node<Integer, Integer>> map;
    DoubleLinkedList<Integer, Integer> doubleLinkedList;

    public LRUCacheDemo(int size) {
        this.cacheSize = size;
        map = new HashMap<>();
        doubleLinkedList = new DoubleLinkedList<>();
    }
    public int get(int key){
        if(!map.containsKey(key)){
            return -1;
        }
        Node<Integer, Integer> node = map.get(key);
        doubleLinkedList.removeNode(node);
        doubleLinkedList.addHead(node);
        return node.value;
    }
    public void put(int key,int value){
        if (map.containsKey(key)){
            Node<Integer,Integer> node = map.get(key);
            node.value = value;
            map.put(key, node);
            doubleLinkedList.removeNode(node);
            doubleLinkedList.addHead(node);
        }else{
            if(map.size() == cacheSize){//坑位满了
                Node<Integer,Integer> lashNode = doubleLinkedList.getLast();
                map.remove(lashNode.key);
                doubleLinkedList.removeNode(lashNode);
            }
        }
        //才是新增
        Node<Integer, Integer> newNode = new Node<>(key, value);
        map.put(key, newNode);
        doubleLinkedList.addHead(newNode);
    }

    public static void main(String[] args) {
        LRUCacheDemo lruCacheDemo = new LRUCacheDemo(3);
        lruCacheDemo.put(1, 1);
        lruCacheDemo.put(2, 2);
        lruCacheDemo.put(3, 3);
        System.out.println(lruCacheDemo.map.keySet());
        lruCacheDemo.put(4, 1);
        System.out.println(lruCacheDemo.map.keySet());

        lruCacheDemo.put(3, 1);
        System.out.println(lruCacheDemo.map.keySet());
        lruCacheDemo.put(3, 1);
        System.out.println(lruCacheDemo.map.keySet());
        lruCacheDemo.put(3, 1);
        System.out.println(lruCacheDemo.map.keySet());
        lruCacheDemo.put(5, 1);
        System.out.println(lruCacheDemo.map.keySet());


    }
}
